Induction-motor.



H. L. BARNHOLDT.

INDUCTION MOTOR. APPLICATION FILED 00131, 1907.

91 9,524, Patented Apr. 27, 1909.

Inventor: Harold L. Barnholdjc,

HAROLD L. BARNHOLDF, OF Pl'lTSFl entrain 3: ND TI OLlPIGN Application filed. Gctober 31, 1937'.

eration of the motor when up to speed.

The squirrel-cage winding, which ordinarily used in induction motors that are not l'tqllll'tftl tostart. under load,posses.--'es marked advantages in simplicity and economy of mst-ruction, but. the starting torque of a squirrel-cage motor is comparativelylow and the starting current is comparatively high. It is known that by cutting the end-rings of a squirrel-cage motor, so as to interrupt their continuity at a number oi points, the starting torque ol the lilOiOl may he in creased and the startin current diminished but cutting the end-rings has bad eli'ect on the operation of the motor when up to speed, for it increases the slip and reduces the ctticiency,-that is, its effect hoth at starting and at full speed. is similar to that produced by increasing the ohmic rt istance of the winding. By my invention the advantages of cutting the cnd-rings are obtained at starting without in'ipairing the toll-speed. operation.

My invention consists in cutting the endrings and providing means for ciosing the breaks in the end-rings when the motor is up to speed. This may be accomplished automatically by employing centrit'ugal contacts adapted to bridge the breaks in the endrings.

My invention will best he understood by reference to the accompanyin drawing in which Figure 1 shows a diagrammatic end View of an induction motor arranged in accordance. with my invention, and 2 is a: perspective View of the squirrel-cage winding.

in the drawing. It represents the stator or Specification 01' Letters Patent.

OTU'E lPntented April 27', 1909.

Serial No. QOLBGIG.

the n'iotor, which is of t i a two-phase four-pole wn provided wi i' b a.

it represents the rotor or :ondary n1emher, which carries a squirrel-cage winding C. The end-riags of this winding are cut at a. plurality of points indicated at r7, and centritugally-actuated contacts I are carried by the rotor, which are adapted to be thrown out "ard by centrifugal force whenthe motor is up to speed, so as to bridge the breaks the end-riugs With this construction the advantages oi cut end-rings are obtained at starting. while at Full speed the motor operates as though the end-rings were continuwars, as in the standard siniirrel-cage motor.

in the drawings 1 ha \e shown one cut per pair of poles in each end-ring, butv I do not limit myself to this number. it. have'tound by test that the greater the number of cuts in the mid-rings, the smalle is the startingcurrent, but it the number of cuts is too great, the starting torque also falls off ranidly. The number oi cuts in each case will he "proportioned to the service. required of the motor.

it do not desire to limit myself to the particular construction and arrangement of parts here shown, but aim in the appended claims to cover all modifications which'ere within the scope of my invention. I

What i claim as new, and desire to secure by Letters Patent of the United States, is,

1. in induction motor having on its secondary member a single squirrel-cage Wind ing' with end-rings open-circuited at a plurality of points, said end-rings forming the only connections between the conductors of said winding, and means for closing the breaks in the end-rings when the motor is up to speed. I

An induction motor having on its sec-. ondary member a single squirrel-cage winding with end-rings open-circuited at a plurality ot points. said end-rings forming the only connections between the conductors of saidwinding, and automatic means for closing the breaks in the end-rings when the motor up to speed.

3. in induction motor having on its sec- (uni-1 ,1 member a, single squirrel-cage Winding with end-rings open-circuited at plumy hzmft this :11 day of October, 1907. rsl lty Ofipifil ltv=i,xfisillf l end-lungs formmg 11h HAROLD L BARNHOLDT Qnly csnne-cbmns ,oemeen the conducols or said Winding, and centrifugally-actuated Witnesses: contacts arranged. to bridga she breaks in the '1 EUGENE NEWNHA'M, end-Kings when the motor is up to speed. .23.. Pmmms- 1n witness \vl'ereoi', I have hereunto ssh 

